Background: People in prison experience higher rates of mental illness than the general community, and commonly have cooccurring histories of drug dependence. While patterns of mental health service contacts following prison release have been extensively described, limited research has explored histories of service contacts prior to adult imprisonment. We describe public mental health contacts in the 12 months prior to first adult imprisonment among a cohort of men recruited in prison in Victoria, Australia, with recent histories of injecting drug use (IDU).Methods: Retrospective data from two administrative databases — public mental health service contacts from the Victorian state-wide public mental health database and imprisonment episodes from Corrections Victoria — were linked to primary data from the Prison and Transition Health (PATH) cohort study. We describe patterns of mental health contact episodes (contact days) and contact types, including continuing community care (categorised as non-urgent care) and crisis/emergency contacts (categorised as urgent) in the 12 months prior to participants’ first adult imprisonment.Results: Among 400 participants, 60 (15%) had contact with a mental health service in the year prior to their first adult imprisonment, accounting for 861 contact episodes [median 5; interquartile range (IQR) 2–11]. The median days between last contact and imprisonment was 52 (IQR 7–116) and the median days between contacts was three (IQR 1–7). Of the total contacts, 52% (n=450/861) were for continuing community care and 27% (n=234/861) involved crisis assessment treatment; 42 (70%) participants with mental health service contacts had at least one crisis/emergency contact within one year of their first adult imprisonment. ­Conclusion: We found that 15% of a cohort of men with histories of IDU had mental health service contacts in the 12 months prior to their first adult imprisonment. These contacts were typically frequent and more than one in four involved crisis/emergency care. These findings highlight significant vulnerabilities and potential missed opportunities for intervention early in offending trajectories. Further research is required to understand how these vulnerabilities can be better identified and more appropriately addressed in-community to reduce pathways into prison.